Integrated circuit fabrication requires the delineation of accurate and precise patterns on substrates. These patterns define the area for doping and internal connections. Lithography is the process whereby a pattern is transferred into a reactive polymer film (a resist) and transfer of that pattern, via methods such as etching, into the underlying substrate. Several forms of lithographic strategies exist. These are short wavelength photolithography, x-ray lithography, electron beam lithography and ion beam lithography. The invention has its primary application to electron and ion beam lithography.
Electron beam lithography can achieve submicron pattern definition, is highly accurate and has low defect densities. The major problems with current electron beam methods are the low throughput density and high cost. Ion beam methods offer the advantage of improved resolution as ions do not scatter as much as electrons when passing through the resist. A major disadvantage of the ion beam method is also the slow speed of those systems in addition to the lack of stable sources with high currents.
Problems existing with prior lithographic systems include accuracy, speed and the amount of capital investment required. The instant invention with its novel structure improves lithography system performance in these areas.